01-08-2018 Council Meeting Packet

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CRITICAL DURATION FLOOD EVENT. The 100-year precipitation or snow melt event with a duration resulting in the maximum 100-year return period water surface elevation. The CRITICAL DURATION FLOOD EVENT is generally either the 100-year, 24 hour rainfall event as found in NOAA Atlas 14 or the ten-day snow melt event assumed to be 7.2 inches of runoff occurring on frozen ground (CN=100); however, other durations (e.g., 6-hour) may result in the maximum 100-year return period water surface elevation. DETENTION BASIN. Any natural or man-made depression that stores stormwater runoff temporarily. DEVELOPMENT. Any land-disturbing activity resulting in creation or reconstruction of impervious surface including, but not limited to, municipal road construction. Normal farming practices part of an ongoing farming operation shall not be considered a DEVELOPMENT. DRAINAGE SYSTEM. A system of open channel, pipe or tile, to drain property, including laterals, improvements, and improvements of outlets, which may or may not be a public system under the jurisdiction of a watershed district under M.S. Chs. 103B, 103D, or 103E. EMERGENCY OVERFLOW (EOF). A primary overflow to pass flows above the design capacity around the principal outlet safely downstream without causing flooding. EROSION AND SEDIMENT CONTROL PLAN. A plan of BMPs or equivalent measures designed to control runoff and erosion and to retain or control sediment on land during the period of land disturbance in accordance with the standards set forth in this chapter. EROSION PREVENTION. Measures employed to prevent erosion including, but not limited to, soil stabilization practices, limited grading, mulch, temporary or permanent cover, and construction phasing. EXCAVATION. The displacement or removal of soil, sediment or other material. FILTRATION. A stormwater quality BMP that uses either natural media such as soil or vegetation or manufactured media to trap pollutants such as nutrients and particles in surface water. FINAL STABILIZATION. All soil disturbing activities at the site have been completed and all soils have to be stabilized by a uniform perennial vegetative cover with a density of 70% over the entire pervious surface area, or other equivalent means necessary to prevent soil failure under erosive conditions. FLOODPLAIN. The areas adjoining a waterbody that are inundated during the 100-year flood. FLOODWAY. The channel of a watercourse, the bed of water basins and those portions of adjoining floodplains that must be kept free of encroachment to accommodate the 100-year flood. FLOODWAY FRINGE. The area between the floodway and the boundary of the 100-year flood. FREEBOARD. Vertical distance between the 100-year flood elevation or emergency overflow elevation of a water basin or watercourse and the elevation of the regulatory elevation of a structure. IMPERVIOUS SURFACE. A compacted surface or a surface covered with material (i.e., gravel, asphalt, concrete, Class 5, etc.) that increases the depth of runoff compared to natural soils and land cover. Including but not limited to roads, driveways, parking areas, sidewalks and trails, patios, tennis courts, basketball courts, swimming pools, building roofs, covered decks, and other structures. INFILTRATION. Water entering the ground through the soil. LAND-DISTURBING ACTIVITY. Any disturbance to the ground surface that, through the action of wind or water, may result in soil erosion or the movement of sediment into waters, wetlands or storm sewers or onto adjacent property. LAND-DISTURBING ACTIVITY includes but is not limited to the demolition of a structure or surface, soil stripping, clearing, grubbing, grading, excavating, filling and the storage of soil or earth materials. The term does not include normal farming practices as part of an ongoing farming operation.